MYELINATED NERVE-FIBER REGENERATION IN DIABETIC SENSORY POLYNEUROPATHY - CORRELATION WITH TYPE OF DIABETES

Observations were made on myelinated fibre regeneration in diabetic se nsory polyneuropathy assessed in sural nerve biopsy specimens. These c onfirmed that regenerative clusters initially develop within abnormall y persistent Schwann cell;basal laminal tubes. The number of regenerat ing fibres, identified by light microscopy, was found to decline in pr oportion to the reduction in total myelinated fibre density. The relat ive number of regenerating fibres was significantly greater in patient s with insulin-dependent as compared with those with non-insulin-depen dent diabetes after correction for age. There was a slight negative co rrelation between the relative proportion of regenerating fibres and a ge, but this was not statistically significant. The progressive reduct ion in the number of regenerating fibres with declining total fibre de nsity indicates that axonal regeneration fails with advancing neuropat hy. The production of nerve growth factor (NGF) and NGF receptors by d enervated Schwann cells is likely to be important for axonal regenerat ion. To investigate whether the failure of axonal regeneration could b e related to a lack of NGF receptor production by Schwann cells, we ex amined the expression of p75 NGF receptors by Bungner bands immunocyto chemically. In comparison with other types of peripheral neuropathy, p 75 NGF receptor expression appeared to take place normally. It is conc luded that failure of axonal regeneration constitutes an important com ponent in diabetic neuropathy. Its explanation requires further invest igation.